Patent GB-616566-A (GB)
Title: Improvements in or relating to colour photography
IPC: G03C7/392
Filed: 1946-08-16
Abstract: 616,566. Colour photography. DU PONT DE NEMOURS & CO., E.I. Aug. 16, 1946, No. 24394. Convention date, Aug. 23, 1945. [Class 98 (ii)] In the production of a coloured photographic image in material containing a reducible silver salt image by colour development to form a quinoneimine or azomethine dye image with subsequent removal of developed silver and undeveloped silver salt, the material is treated, prior to such removal of silver and silver salt with an aldehyde or ketone containing a solubilizing group, e.g. benzaldehyde-o-sulphonic acid and its sodium salt; benzaldehydem- and -p-sulphonic acids, phthalaldehydic acid, glyoxylic acid, 1-naphthaldehyde-2- and - 4- sulphonic acids, 1-naphthaldehyde-4-carboxylic acid, 2-naphthaldehyde-3-sulphonic acid, 2-naphthaldehyde-3-carboxylic acid, pymeric acid, and laevulinic acid and their alkali metal and ammonium salts; hydroxybenzaldehyde; the amide of phthalaldehydic acid; and benzaldehyde-o-sulphonamide. In example 1, pieces of exposed multilayer material consisting of a cellulose acetate support successively coated with a gelatin dispersion of colloidal silver and the mixed acetal of salicylaldehyde and benzaldehyde-o-sulphonic acid with polyvinyl alcohol, a red-sensitive but green-insensitive gelation-silver halide emulsion, a gelatin dispersion of 4 : 4<1>-o-sulphobenzylidene - bis - (1 - phenyl - 3 - methyl - 5 - pyrazolone), a green-sensitive gelatino-silver iodobromide emulsion, a gelatin dispersion of yellow colloidal silver and 4 : 4<1>-o-sulphobenzylidene-bis-(1- phenyl-3-methyl-5-pyrazolone), a gelatin dispersion of benzoylacet-furoylacet-benzidide, and a blue-sensitive gelatino-silver iodobromide emulsion are developed in a metol-hydroquinone developer, washed, dried, re-exposed to white light, and colour developed. One piece is washed and silver and silver salts removed by successive treatments in potassium ferricyanide and hypo baths, and two other pieces are bathed in aqueous sodium benzaldehyde-o-sulphonate before washing and further treatment. Stain is reduced or removed by the treatment. In example 2, exposed material consisting of a cellulose nitrate support successively coated with a gelatin dispersion of colloidal silver, a gelatin dispersion of 4 : 5<1>-bis-(1-naphthol-2- sulphamidophenyl)-ether, a red-sensitive but green-insensitive gelatino-silver iodobromide emulsion, a gelatin dispersion of 4 : 4<1>-bis-(1- naphthol-2-sulphamidophenyl)-ether, a gelatin dispersion of 4 : 4<1>-o-sulphobenzylidene-bis-(1- phenyl-3-methyl-5-pyrazolone), a green-sensitive gelatino-silver iodobromide emulsion, a gelatin dispersion containing colloidal silver and 4 : 41 - o - sulphobenzylidene - bis - (1 - phenyl- 3-methyl-5-pyrazolone), a gelatin dispersion of benzoylacet-furoylacet-benzidide, and a bluesensitive gelatino-silver iodobromide emulsion is developed in a metol-hydroquinone developer including KOH and KCNS, washed, dried, re-exposed to white light, and colour developed in a colour developer including KCNS and benzaldehyde-o-sulphonic acid. In example 3, a film as in example 2 is treated after the first development with an aqueous solution of benzaldehyde-o-sulphonic acid. In example 4, exposed material consisting of a film support coated with a silver iodobromide emulsion having as binder the salicylaldehyde acetal of polyvinyl alcohol is colour developed in a developer including benzaldehyde-o-sulphonic acid. In example 5, stop baths contain benzaldehyde-o-sulphonic acid and sodium sulphite, or sodium acetate and acetic acid, or sodium bisulphite. A fixing bath contains hypo, sodium sulphite, boric acid, acetic acid, potassium alum, and benzaldehyde-o-sulphonic acid. Specifications 2562/13, [Class 98 (ii)], 544,189, 551,116, 554,302 and 598,477 are referred to.